Avoid python 2 and hardcoding the clang version in the icu4c

The clang keeps get updated, and the hardcoded version in the script
gets outdated quicly, and the script stopped working.

Avoid hardcoding the version, and so the script should keep working
even though clang is updated.

Also, print the clang version in the script.

Test: ./generate_ndk.py
Change-Id: Ia5cfd2db9af5a75f93cb54a78363076c973c8303
3 files changed